General Characteristics Of Thoracic Outlet Syndrome

The thoracic outlet syndrome is a constellation of neurovascular symptoms resulting from compression at the thoracic outlet. Ninety-five percent of thoracic outlet syndromes result from neurologic symptoms usually from compression of the lower roots of the brachial plexus. Only 5% of the thoracic outlet syndrome is vascular in etiology. The brachial plexus consists of input from C5, C6, C7, C8 and T1. The most common cause of the thoracic outlet syndrome results from compression of the lower roots of the brachial plexus, i.e. the ulnar distribution contributed to from C8 and T1.

The thoracic outlet is that region bordered by the clavicle and first rib (Fig. 22.1). Posteriorly, it is bounded by the scalene medius and the long thoracic nerve. The anterior scalene inserting on scalene tubercle of first rib divides the thoracic outlet into an anterior compartment containing the subclavian vein, and the posterior compartment containing the subclavian artery and the brachial plexus. The most common cause of the thoracic outlet syndrome is a cervical rib. This occurs in about 95% of patients with the syndrome. Other bony abnormalities may exist and contribute to the thoracic outlet syndrome. This includes rudimentary first ribs or fusion of the first and second ribs, clavicular deformities or first rib fractures. First rib anomalies are often related to vascular cause of thoracic outlet syndrome (Fig. 22.2a-c).

There are several tests used to mimic the findings of the thoracic outlet syndrome. Most of these are neither sensitive nor specific and generally are of questionable value but will be included here for completeness. Perhaps the most useful of all these tests is the Roos test.